1. Field of the Invention
The present invention relates to a multiplexer and a parallel/serial converter for differential signals.
2. Description of the Related Art
In recent years, in order to transmit a video signal or an audio signal between multiple electronic devices, high-speed differential interfaces such as HDMI (High-Definition Multimedia Interface) or DVI (Digital Visual Interface) are employed. For example, a TV includes multiple HDMI input ports, selects one of the signals input to these HDMI input ports, and displays the signal thus selected on a display panel. In order to select one differential signal from among multiple differential signals, a multiplexer (multiple input, single output selector) is employed.
FIGS. 1A and 1B are circuit diagrams each showing an example configuration of a five input, one output multiplexer. A multiplexer 500 includes five input ports Pi1 through Pi5, a single output port Po, and two input, one output selectors (switches) 5021 through 5026 connected in tournament form. The selectors 5021 through 5026 each include two differential input terminals D1 and D2, and a single differential output terminal Do. When a corresponding control signal sel is high level, each selector 502 selects a differential signal input to the first input terminal D1. When the corresponding control signal sel is low level, the selector 502 selects a differential signal input to the second input terminal D2. Each selector 502 outputs the signal thus selected via the output terminal Do.
One of the signals input to the input ports Pi1 through Pi5 is output via the output port Po according to the combination of the values of the control signals sel0 through sel5. The selectors 5023 and 5024 do not perform any substantial selection operation, but are each arranged to make the propagation delay amounts uniform over all the paths.